我想用gitlab-ci运行deploy脚本，但是步骤ssh-add $SSH_PRIVATE_KEY 会返回错误：

echo "$SSH_PRIVATE_KEY" | ssh-add -
Error loading key "(stdin)": invalid format

你可以看到我的 .gitlab-ci.yml ：

deploy:
  image: node:9.11.1-alpine
  stage: deploy
  before_script:
    # Install ssh-agent if not already installed, it is required by Docker.
    # (change apt-get to yum if you use a CentOS-based image)
    - 'which ssh-agent || ( apk add --update openssh )'

    # Add bash
    - apk add --update bash

    # Add git
    - apk add --update git

    # Run ssh-agent (inside the build environment)
    - eval $(ssh-agent -s)

    # Add the SSH key stored in SSH_PRIVATE_KEY variable to the agent store
    - echo "$SSH_PRIVATE_KEY"
    - echo "$SSH_PRIVATE_KEY" | ssh-add -

    # For Docker builds disable host key checking. Be aware that by adding that
    # you are suspectible to man-in-the-middle attacks.
    # WARNING: Use this only with the Docker executor, if you use it with shell
    # you will overwrite your user's SSH config.
    - mkdir -p ~/.ssh
    - '[[ -f /.dockerenv ]] && echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config'
    # In order to properly check the server's host key, assuming you created the
    # SSH_SERVER_HOSTKEYS variable previously, uncomment the following two lines
    # instead.
    # - mkdir -p ~/.ssh
    # - '[[ -f /.dockerenv ]] && echo "$SSH_SERVER_HOSTKEYS" > ~/.ssh/known_hosts'
  script:
    - npm i -g pm2
    - pm2 deploy ecosystem.config.js production
  # only:
  # - master

在我的项目设置中，我已经添加了SSH_PRIVATE_KEY变量，其生成服务器的id_rsa为 cat ~/.ssh/id_rsa.pub .

有人可以帮帮我吗？

gitlab gitlab-ci